The present invention is an in-situ apparatus for generating carbon dioxide gas at an oil site for use in enhanced oil recovery (EOR). The apparatus includes a steam generator adapted to boil and superheat water to generate a source of superheated steam, as well as a source of essentially pure oxygen. The apparatus also includes a steam reformer adapted to react a carbonaceous material with the superheated steam and the pure oxygen, in an absence of air, to generate a driver gas comprising primarily carbon dioxide gas and hydrogen gas. A separator is adapted to separate at least a portion of the carbon dioxide gas from the rest of the driver gas to generate a carbon dioxide-rich driver gas and a hydrogen-rich fuel gas. A compressor is used for compressing the carbon dioxide-rich driver gas for use in enhanced oil recovery, and the compressed carbon dioxide-rich driver gas, with substantially no oxygen, is injected to a predetermined depth in order to enhance oil recovery at the oil site. Unlike traditional CO2-EOR, which requires large power plants stationed near metropolitan areas and expensive pipeline networks, the in-situ apparatus can be placed or constructed at the site of the oil field, while a portion of the carbonaceous material may be obtained from a site outside the oil field.